Writing in the Sunday Times, he said it was horrifying that the perpetrator "could have been brought up in Britain".

He said the Government was investing "significant resources" to tackle "a barbaric ideology", warning if the IS militants are not stopped in Iraq and Syria "sooner or later they will seek to strike us on British soil".

Mr Hammond said the threat from Iraq and Syria would last a generation, echoing comments made by Home Secretary Theresa May as she announced plans to bring in new laws to tackle the threat of British jihadists.

Video:Peshmerga Fighters Battle IS Forces

But former shadow home secretary David Davis dismissed suggestions the new laws, dubbed asbos for terrorists, would stop Britons fighting for IS, also known as ISIS and ISIL.

Instead, he said, the jihadists should be stopped from returning to the UK and stripped of their citizenship.

Mr Davis said the Government's response to the crisis in Iraq had been "tentative, uncertain, almost limp".

Lord Carey, the former Archbishop of Canterbury, also called for Britons fighting for IS in Iraq and Syria to lose their passports.

He wrote in the Mail on Sunday: "They should not have access to the privilege of travelling under a British passport... and they certainly should not be able to travel back with the barbaric and bloodthirsty skills they have gained."

The Home Office has insisted it would take the "strongest possible action" against people travelling to fight in Iraq and Syria.

Video:'Asbos For UK Jihadi Extremists'

A spokesman said: "The police, security services and Border Force are actively working to identify, detect and disrupt terrorist threats, including from British fighters attempting to return to the UK.

"They use a wide range of powers including those which allow them to detain and interview individuals at the UK border suspected of being involved in terrorism."